Methacrylic resin composition and injection-molded article

Active Publication Date: 2019-02-14
KURARAY CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0015]The methacrylic resin composition of the present invention has excellent flowability and is less likely to cause molding defects such as silver streaks, cracks, sink marks, flow marks, resin burning, gas contamination, or coloring. The methacrylic resin composition of the present invention is also suitable for injection molding. The methacrylic resin composition of the present invention is also suitable for obtaining a thin shaped product, for example, a board having a thickness of 1 mm or less. A shaped product formed of the methacrylic resin composition of the present invention has high heat resistance and high mechanical strength and has no appearance defect such as coloring. The methacrylic resin composition of the present invention generates low shear heat when injection-molded and can be injection-molded even at low temperature and high injection pressure. Thus, a shaped product having good appearance is obtained.
[0016]A methacrylic resin composition of the present invention comprises a methacrylic resin. The content of the methacrylic resin in the methacrylic resin composition of the present invention is not less than 90% by mass, preferably 90 to 99.9% by mass, more preferably 90 to 99.5% by mass.
[0017]A methacrylic resin used in the present invention comprises methyl methacrylate m

Problems solved by technology

However, application of these methods to a methacrylic resin would cause re

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Example

EXAMPLES 1 TO 4 AND COMPARATIVE EXAMPLES 1 TO 8

[0100]Purified methyl methacrylate (MMA), methyl acrylate (MA), 2,2′-azobis(2-methylpropionitrile) (AIBN), and n-octyl mercaptan (n-OM) were charged into a stirrer-equipped autoclave A at ratios described in Tables 1 and 2 and dissolved uniformly to obtain starting material liquids (I).

[0101]The starting material liquid (I) was fed from the autoclave A to a tank reactor whose temperature was controlled to 140° C., at 1.5 kg / hr. Bulk polymerization was performed for a mean residence time of 120 minutes, and the reaction solution containing a polymer was continuously discharged from the tank reactor. The polymerization conversion ratio of the obtained polymer was 57% by mass.

[0102]Then, the reaction solution was heated to 230° C. and fed to a twin-screw extruder whose temperature was controlled to 240° C. A volatile component containing unreacted monomers as a main component was separated and removed in the twin-screw extruder, and the po...

Example

COMPARATIVE EXAMPLE 9

[0103]Purified methyl methacrylate, methyl acrylate, 2,2′-azobis (2-methylpropionitrile), and n-octyl mercaptan were charged into a stirrer-equipped autoclave A at a ratio described in Table 2 and dissolved uniformly to obtain a starting material liquid (I).

[0104]Also, 2,2′-azobis (2-methylpropionitrile) and n-octyl mercaptan were charged into an autoclave B at a ratio described in Table 2 and dissolved with a slight amount of methyl methacrylate to obtain a starting material liquid (II).

[0105]The starting material liquid (I) was fed to a first tank reactor whose temperature was controlled to 140° C., at 1.5 kg / hr, and bulk polymerization was performed for a mean residence time of 90 minutes. A reaction solution (a) containing a polymer was continuously discharged from the first tank reactor at 1.5 kg / hr. The polymerization conversion ratio of the obtained polymer was 35% by mass, and the degree of polymerization was 870.

[0106]The reaction solution (a) held at 1...

Example

[0108]Resin pellets were obtained in the same manner as in Example 1 except that when separating and removing a volatile component containing unreacted monomers as a main component in the twin-screw extruder and extruding a polymer as a strand, 0.40 part by mass of stearyl alcohol and 0.10 part by mass of stearic acid monoglyceride were added to 100 parts by mass of the polymer. With respect to the resin pellets, the weight-average molecular weight Mw, the molecular weight distribution Mw / Mn, the ratio W of MA units, the degree of polymerization P, the melt flow rate R, and the yellow index difference ΔYI were measured. Also, the resin pellets were evaluated for injection moldability, flowability, and mold stain. The results are shown in Table 2.

TABLE 2Comp. Ex.45678910Starting material liq.(I)MMA [parts by mass]94.296.096.094.294.294.294.2MA [parts by mass]5.84.04.05.85.85.85.8n-OM [part by mass]0.620.620.350.330.360.360.54AIBN [part by mass]0.0060.0060.0060.0060.0060.0040.006Start...

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Abstract

A methacrylic resin composition comprising not less than 90% by mass of a methacrylic resin, wherein the methacrylic resin comprises 95 to 100% by mass of methyl methacrylate monomer units and 0 to 5% by mass of acrylate monomer units, the methacrylic resin has an Mw of 57000 to 90000, Mw representing a weight-average molecular weight, and a ratio Mw/Mn of not more than 1.9, Mn representing a number-average molecular weight, the methacrylic resin composition has an absolute value of a difference between YI4 and YI2 of not more than 3, YI4 representing a yellow index at an optical path length of 200 mm of an injection-molded article obtained at a cylinder temperature of 280° C. in a molding cycle of 4 minutes, YI2 representing a yellow index at an optical path length of 200 mm of an injection-molded article obtained at a cylinder temperature of 280° C. in a molding cycle of 2 minutes, and meets a relationship represented by Formula (B) and Formula (C):
R≥11   Formula (B)
0.8<R/E<1.2   Formula (C)
where R represents the melt flow rate of the methacrylic resin composition as measured at 230° C. under a load of 3.8 kg, the melt flow rate R being expressed in g/10 min; and E represents a value calculated by Formula (A), the value E being expressed in g/10 min, the Formula (A) being E=exp (0.17112×W−0.00399×P+5.09713) where W represents the ratio of acrylate monomer units to the total monomer units in the methacrylic resin, the ratio W being expressed in % by mass; and P represents the degree of polymerization of the methacrylic resin.

Description

TECHNICAL FIELD[0001]The present invention relates to a methacrylic resin composition and an injection-molded article, and a production method thereof. More specifically, the present invention relates to a methacrylic resin composition that during heat forming, has excellent flowability and is less likely to be colored and an injection-molded article that has high heat resistance and high mechanical strength, and a production method thereof.BACKGROUND ART[0002]Methacrylic resins have high transparency and are useful as the materials of molded articles used as optical members, lighting members, sign members, decoration members, and the like. There is a demand to lighten or thin shaped products in some fields in which methacrylic resin shaped products are being used. To obtain thin shaped products, the methacrylic resin is required to have high flowability when melted. As commonly known methods for increasing the flowability of a resin include, mentioned can be lowering the softening ...

Claims

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Application Information

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IPC IPC(8): C08L33/12C08L33/08C08F220/14C08F220/18C08F220/06
CPCC08L33/12C08L33/08C08F220/14C08F220/18C08F220/06C08F2500/03C08F2500/01B29C45/0001B29C45/76C08F2/02B29K2033/12B29C2945/76003
Inventor KITADE, YASUHITOOZAWA, HIROSHI
Owner KURARAY CO LTD
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